The balancing of the armor would be really hard with all the customization but in the end it would be completely worth it.
List So Far:
-oxygen
-power reactor modules
- shield rechargers
-hull and hardened hull
-plex storages
-disintegrators...
-leaves and wood for cameo
-lava for physical combat
Let me add these:
-several types of melee weapons : plasma sword, normal sword, punch, various types of weapons, like axes.
-moment assist, jump ,run , jet pack, flight control, walk assist, boost, ect.
-shields, like on ships
-armor plating( ie. the hulls mentioned earlier)
-advanced optics, for helmet
-shields that are hand held
-cloaking
I hope this list becomes much longer. =)